1. Field of the Invention
The invention relates to a method of visually measuring the brightness of ambient lighting surrounding a display device, and more particularly, to a method of visually measuring the brightness of ambient lighting, in which the state of a video display device is set to an optimal gray scale reproduction state, an image with brightness corresponding to one selected from a plurality of brightness stages is displayed to the user, the user selects a brightness stage corresponding to an image having brightness that is the most approximate to the brightness of ambient lighting, and a brightness value corresponding to the selected brightness stage is determined as the brightness of ambient lighting around a display device being used.
2. Description of the Related Art
Color management systems are generally used to achieve color matching between an input device and an output device. Color management systems use various color transformation methods for color matching, by referring to the color characteristics of each of the input device and the output device. The color and brightness of ambient lighting affect the perceived color produced by a display device. Recently color management systems are considering ambient lighting for color matching.
To achieve color matching, a color management system requires the color characteristics of each input or output device, which are obtained from a profile that is a computer program file that describes color characteristics. The profile has a specific format. For example, to achieve color matching between a display device and a color reproduction apparatus, a color management system requires a profile of the display device.
A display device manufacturer may provide a color characteristic profile that can be applied in a fixed state of ambient lighting. As such, a color management system can only use the color characteristic profile under a single color characteristic condition of a display device that is set by the display manufacturer. However, the color characteristic condition of a display device set by a display manufacturer does not meet the demand of various users for a color characteristic change. When ambient lighting is changed due to a change in an environment where the display device is used, the perceived color characteristics of the display device are changed. However, the color characteristic profile set by a display manufacturer does not reflect the change of the color characteristics of a display device. Hence, color matching between an input device and an output device is difficult.
U.S. Pat. No. 5,499,040 discloses a conventional technique in which devices known as calorimeters, photometers, or spectroradiometers are used to measure changes in the color characteristics of a display device that have been made due to a change in an environment where the display device is used or by the user. The measurements using these devices provide an accurate result. However, these devices are expensive and installation and operation of the devices is inconvenient. Therefore, an ordinary user of a display device cannot easily manipulate these devices.
There remains a need for a simple and inexpensive method to visually measure the color characteristics of a display device and those of ambient lighting. Examples of this method are disclosed in U.S. Pat. Nos. 5,638,117, 5,791,781, 5,870,069, 5,956,015, and 6,078,309. However, in the methods disclosed in U.S. Pat. Nos. 5,638,117, 5,791,781, 5,870,069, and 5,956,015, a separate color matching card is used to measure the color characteristics of ambient lighting and the color temperature of a display device, which causes additional cost. Also, U.S. Pat. No. 6,078,309 still does not propose a method to obtain the color and brightness characteristics of ambient lighting.